like this can be, you know, little things like the main jugular vein, extensive sweating in a cold environment. they're focused on what they're doing. they don't fit in with the crowd. so this is a way of actually, without the technology, but with the civilians or police or law enforcement officers actually looking for suspects in a crowd, these are some ways that you can actually find and detect a suspect like this. >> mike: you've been the pictures of the boston suspects. would they have given you cause for concern just by their appearances, the way they were behaving? >> no doubt, no doubt. immediately after the events, obviously, i was watching the video stream coming through. you can see that the crowd watching the finish of the boston marathon are watching the runners whereas these two were not watching the marathon at all. you know, they were very focused on where they were going. one was walking after the other, in a hurry, it seemed. their dress, their stride, the walk. there's a specific walk that a suspect of this nature has. a characteristic that a normal person, under normal circu